Rice professor: Granite countertops may cause you harm

Be wary of granite that glowsRice professor says countertops may be tainted with uranium

Last August, Consumer Reports magazine — ever alert to stylish trends among its affluent readers — pinpointed the growing popularity of natural stone countertops, demand for which had increased 5 percent annually for the previous five years. But for Rice University physics professor W.J. Llope, the article's title, "Countertops: The Hottest Rocks," carried an unsettling irony.

Some granite countertops, he says, contain high levels of uranium, which, by generating gamma radiation and radon gas, can endanger human health.

"Most stones, in terms of radioactivity, are relatively quiet," Llope said. "But there are a couple I have found that are insanely hot."

Using a Rice University spectrometer, Llope has examined 55 stones, representing about 25 varieties of granite purchased from Houston-area dealers. Some, he said, could expose homeowners to 100 millirems of radiation — the annual exposure limit set by the Department of Energy for visitors to nuclear labs — in just a few months.

Llope, who said he plans to publish his findings in a peer-reviewed journal, declined to name the most hazardous varieties of granite he has thus far examined. But he said dangerously radioactive varieties include striated granites from Brazil and Namibia.

As many as 1,600 varieties of granite from 64 countries are sold for household use in the United States. None of them is routinely tested for radioactivity.

Still, he said, his organization is assembling a panel of scientists to develop a protocol for testing granite for radioactivity. He said that panel should be in place by summer's end.

"There's been a lot of junk science passed off as real science," Martinez said. "We want to establish scientific standards and protocol that would allow consistent testing in a logical way."

The trade group said reports of granite's radioactivity have been sensationalized by competitors who market non-granite products.

Llope hailed the group's move to test granite as an important first step in ensuring customer safety.

"There should be some oversight in this," Llope said. "This is something the Environmental Protection Agency or the dealers or both of them should do. This isn't something customers should have to do, not something they should have to lay awake worrying themselves to death about. They need help."

The EPA, although it offers the public information on radon hazards, has no authority to regulate quality of indoor air.

Llope said the radioactive substances in granite, significantly uranium, pose a double threat to homeowners: radiation and radon gas. Radiation exceeding levels an individual routinely receives just living on Earth can contribute to cancer. Radon is second only to cigarettes as a cause of lung cancer. It is especially dangerous to smokers.

"Where you have radon," Llope said, "you have radiation."

Llope said that slabs of stone taken from the same quarry — even different sections of the same slab — may differ in radiation levels.

In addition to his study of granite purchased in Houston, Llope studied 20 peer-reviewed journal articles reporting on the results of radiation testing of 95 granite samples. Llope found three cases where the stones generated levels of radon deemed dangerous by EPA.

"I'm not claiming that people necessarily will get very sick or die of cancer within months," he said, "but if you spend 10 years in that kitchen there is a risk you may end up with cancer. It might or might not be attributed to granite. Who would know?"

Llope advised homeowners to test their granite countertops for radon. Inexpensive test kits can be found at hardware stores.